I propose to extend our investigations of Candida antigenemia to develop sensitive, specific immunoassays to diagnose invasive infections. Specific aims of our study will be: 1) To improve the sensitivity of the radioimmunoassay to C. albicans mannan by developing more efficient extraction procedures, by obtaining a higher affinity antibody, and by employing an intrinsically labeled antigen. 2) To develop RIAs to relevant Candida mannans. If one immunoassay is not adequately cross-reactive to the major antigenic groups, a combination of RIAs will be needed; one for mannans from C. albicans, group A/c. tropicalis, and one for C. albicans, group B/c. stellatoidea. 3) To evaluate the RIA(s) prospectively in a blinded patient trial. Thus we can develop rigorous criteria for the diagnostic predictive value and prognostic usefulness of antigen RIAs and for assays for Candida antibody. 4) To develop immunoassay(s) to mannan which will be more generally applicable to clinical serologic laboratories. We will adapt ELISA, or sensitive immunoprecipitin techniques to this end. 5) To develop antigen immunoassays to other Candida antigens. This work will be approached two ways. We will examine glucan and two other polysaccharides, identified in lysozyme and pepsin digests of washed Candida cell walls. Also we will develop immunoassays to three cytoplasmic antigens that were mamor immunogens during systemic infection. 6) To quantitate humoral responses to Candida antigens other than mannan. This can be accomplished by reference to standard curve titrations, using immunochemical reagents generated for the reference to standard curve titrations, using immunochemical reagents generated for the antigen RIAs. Changes in monospecific antibody concentrations will be examined for significance. 7) To test the newly developed assays in animal models of invasive candidiasis. Promising assays will be further evaluated (a) retrospectively in a panel of sera already obtained and (b) prospectively in hospital patients suspected of fungal infections. 8) To characterize the significance, if any, of Candida antigenemia, immune complexes, and humoral response fr the immunopathogenesis of infection. 9) Finally, to apply the immunochemical techniques, assays and models developed herein to te immunodiagnosis of nocardiosis.